Where have all the big fish gone? How do we get them back?
Fish populations around the globe are in decline and many governments are working on strategies to help them recover. In particular trouble are stocks of tropical reef fish that suffering from the decline in coral reefs and over-fishing. A part of our new strategy is providing protection for special parts of the coastal ocean as we do for special parts of the United States with the National Park System. This is currently being done by the establishment of Marine Protected Areas and Marine Sanctuaries.
Because the idea of protecting parts of the ocean is relatively new, many questions about how best to do it remain. Where should we put protected areas? How big should they be? What bottom types and depths should be included within their boundaries? Scientists from the National Center for Coastal Ocean Science (NCCOS) are working to answer some of these questions at the Gray’s Reef Sanctuary off the coast of Georgia, the Tortugas Ecological Reserve off Florida and in the Bay of La Parguera, Puerto Rico.
The question of what bottom types and water depths should be included in a protected area turns out to be an important one because many fish move from one type of place to another as they grow. Most ocean fish species start out life at a size of about 1/8 of an inch long and grow rapidly during their first year. As they grow the places where they like to eat, swim and hide change. It is important to know what places are important to fishes so that they can be included in protected areas. NCCOS divers are sampling fish populations in the bay of La Parguera, Puerto Rico, by counting and catching them to determine what habitats are important for fish growth movement and survival. Patterns of fish distribution are complicated because they change as fish grow, seasonally and are often different during day and night. For example many important families of reef fish (snappers, grunts, cardinal fish, big eye) rest on coral reefs during the day but at night migrate to soft bottom habitats to feed.
The long term goal of coral reef fish studies is to determine the best combination of habitats to include in a marine protected area to promote natural recovery of fish populations. We have completed a study of some severely depleted reef fish in Puerto Rico so that we can provide boundary recommendations for a protected area designed to bring the big ones back!